What Does AD Stand For? BC, AD, BCE and CE

What does BC and AD stand for, side by side?

So 44 BC and 44 BCE are the same year, and AD 1066 and 1066 CE are the same year. If you can read one system, you can read the other.

Where AD came from

The system of counting years from the birth of Jesus was worked out by a monk named Dionysius Exiguus in the 500s. He wanted a better way to calculate the date of Easter. A couple of centuries later, the English scholar Bede used AD dates in his history writing, which helped spread the system across Europe.

BC came into wide use later, as writers needed a way to count backward for older events. Historians today generally think the starting point was off by a few years, but the numbering stuck, and it is now the standard calendar count for most of the world.

What does BCE stand for, and why do some writers use it?

BCE stands for Before Common Era, and CE stands for Common Era. The labels have been around for a long time and became more common in academic, scientific and school writing. People who prefer them say they work for readers of any faith or none, since the world now shares the same calendar. People who prefer BC and AD say the traditional labels are familiar and historically meaningful.

Both systems are correct, and style guides accept either. The usual advice is to pick one and use it consistently within a single paper, book or exhibit.

How to write the dates correctly

• AD goes before the number in traditional style: AD 800. Because it means "in the year of the Lord," it reads naturally in front. Many writers now put it after, 800 AD, and that is widely accepted.
• BC, BCE and CE go after the number: 300 BC, 300 BCE, 1492 CE.
• Centuries put AD after: "the fifth century AD."
• Periods are optional. B.C. and A.D. are still seen, but most modern style drops them. Some books print the letters in small capitals.

Counting backward in BC

BC years count down toward year 1, so a larger number is further in the past. 500 BC came before 200 BC. To find how many years separate a BC date and an AD date, add them and subtract one, because there is no year zero.

Century names follow the same pattern. The first century AD is years 1 to 100, and the first century BC is 100 BC to 1 BC.

What does AD stand for in job titles and outside of dates?

The letters have everyday meanings that have nothing to do with history.

• AD in job titles: assistant director, associate director, art director or athletic director, depending on the field. A school AD runs the sports programs.
• CE: continuing education credits, civil engineering, or the CE mark on products, from French Conformité Européenne, showing a product meets European safety rules. What does CE stand for in a ship crew list? Usually chief engineer, the officer in charge of the engine room.
• BC: British Columbia, the Canadian province, on maps and addresses.
• ad: in lowercase, short for advertisement.

Other Latin short forms you might see in history books are ca. for circa, meaning about, i.e. for "that is," and a.m. and p.m. for clock times. More familiar letters live on the famous acronyms page.